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Measurements of production cross sections of WZ and same-sign WW boson pairs in association with two jets in proton-proton collisions at 13 TeV
No full textMeasurements of production cross sections of WZ and same-sign WW boson pairs in association with two jets in proton-proton collisions at 13 TeV at the LHC are reported. The data sample corresponds to an integrated luminosity of 137 fb, collected with the CMS detector during 2016-2018. The measurements are performed in the leptonic decay modes WZ and WW, where e, . Differential fiducial cross sections as functions of the invariant masses of the jet and charged lepton pairs, as well as of the leading-lepton transverse momentum, are measured for WW production and are consistent with the standard model predictions. The dependence of differential cross sections on the invariant mass of the jet pair is also measured for WZ production. An observation of electroweak production of WZ boson pairs is reported with an observed (expected) significance of 6.8 (5.3) standard deviations. Constraints are obtained on the structure of quartic vector boson interactions in the framework of effective field theory
A quantum framework for AdS/dCFT through fuzzy spherical harmonics on S
No full textWe consider a non-supersymmetric domain-wall version of = 4 SYM theory where five out of the six scalar fields have non-zero classical values on one side of a wall of codimension one. The classical fields have commutators which constitute an irreducible representation of the Lie algebra (5) leading to a highly non-trivial mixing between color and flavor components of the quantum fields. Making use of fuzzy spherical harmonics on S, we explicitly solve the mixing problem and derive not only the spectrum of excitations at the quantum level but also the propagators of the original fields needed for perturbative quantum computations. As an application, we derive the one-loop one-point function of a chiral primary and find complete agreement with a supergravity prediction of the same quantity in a double-scaling limit which involves a limit of large instanton number in the dual D3-D7 probe-brane setup
Investigations on the Capabilities of THz Production at the PITZ Facility
No full textThe European XFEL has planned to perform pump-probe experiments by using its x-ray pulses and THz pulses. A promising concept to provide the THz pulses is to generate them using a tunable high-power accelerator-based THz source. The Photo Injector Test Facility at DESY in Zeuthen (PITZ) can serve as a prototype for the development of the THz source. This thesis investigates the capabilities to generate THz pulses using electron bunches from the PITZ accelerator and three methods of THz radiation generation including Self-Amplification of Spontaneous Emission Free-Electron Lasers (SASE FELs), Coherent Transition Radiation (CTR), and Coherent Diffraction Radiation (CDR).Studies of the THz SASE FEL using 4 nC electron beams and an APPLE-II type undulator with a period length of 40 mm in the helical mode were performed. Start-to-End (S2E) simulations show that FEL pulse energies at 100 m and 20 m wavelengths (corresponding to 3 THz and 15 THz frequencies) of up to 2.5 mJ are achievable. Experimental optimization and characterization of 4 nC electron beams for the SASE FEL option were performed at PITZ. Parameters of the beam, including slice emittance, slice energy spread, and current distribution, were measured. FEL simulations based on measured beam parameters show that the FEL pulse energies are in the sub-mJ level. S2E simulations of the THz radiation generated by CTR and CDR were performed. By using a short Gaussian photocathode laser pulse and an electron bunch compressed by velocity bunching with bunch charge up to 1 nC, CTR and CDR pulse energies up to 4 J and frequencies covering up to 0.4 THz are achievable. Corresponding experimental generations of CTR and CDR were performed successfully. Average pulse energies of up to 1.85 J and coherent frequencies of up to 1.5 THz were measured. Furthermore, S2E simulations and corresponding experiments of the THz radiation generated by using a comb beam were performed. Several narrow-band peaks at higher-order harmonics were observed in the spectral distributions
From boundary data to bound states
No full textWe introduce a — somewhat holographic — dictionary between gravitational observables for scattering processes (measured at the boundary) and adiabatic invariants for bound orbits (in the bulk), to all orders in the Post-Minkowskian (PM) expansion. Our map relies on remarkable connections between the relative momentum of the twobody problem, the classical limit of the scattering amplitude and the deflection angle in hyperbolic motion. These relationships allow us to compute observables for generic orbits (such as the periastron advance ∆Φ) through analytic continuation, via a radial action depending only on boundary data. A simplified (more geometrical) map can be obtained for circular orbits, enabling us to extract the orbital frequency as a function of the (conserved) binding energy, Ω(E), directly from scattering information. As an example, using the results in Bernet al. [36, 37], we readily derive Ω(E) and ∆Φ(J, E) to two-loop orders. We also provide closed-form expressions for the orbital frequency and periastron advance at tree-level and one-loop order, respectively, which capture a series of exact terms in the Post-Newtonian expansion. We then perform a partial PM resummation, using a no-recoil approximation for the amplitude. This limit is behind the map between the scattering angle for a test-particle and the two-body dynamics to 2PM. We show that it also captures a subset of higher order terms beyond the test-particle limit. While a (rather lengthy) Hamiltonian may be derived as an intermediate step, our map applies directly between gauge invariant quantities. Our findings provide a starting point for an alternative approach to the binary problem. We conclude with future directions and some speculations on the classical double copy
Full 3D + 1 modeling of tilted-pulse-front setups for single-cycle terahertz generation
No full textThe tilted-pulse-front setup utilizing a diffraction grating is one of the most successful methods to generate single- to few-cycle terahertz pulses. However, the generated terahertz pulses have a large spatial inhomogeneity, due to the noncollinear phase matching condition and the asymmetry of the prism-shaped nonlinear crystal geometry, especially when pushing for high optical-to-terahertz conversion efficiency. A 3D+1 (x,y,z,t) numerical model is necessary in order to fully investigate the terahertz generation problem in the tilted-pulse-front scheme. We compare in detail the differences between 1D+1, 2D+1 and 3D+1 models. The simulations show that the size of the optical beam in the pulse-front-tilt plane sensitively affects the spatio-temporal properties of the terahertz electric field. The terahertz electric field is found to have a strong spatial dependence such that a few-cycle pulse is only generated near the apex of the prism. Even though the part of the beam farther from the apex can contain a large fraction of the energy, the terahertz waveform shows less few-cycle character. This strong spatial dependence must be accounted for when using the terahertz pulses for strong-field physics and carrier-envelope-phase sensitive experiments such as terahertz acceleration, coherent control of antiferromagnetic spin waves and terahertz high-harmonic generation
Precision predictions for Lepton Collider Top Quark Physics
No full textIn this talk I will briefly review the physics program of plannede+e- colliders. I will focus on certain aspects of the top physicsprogram of these machines to determine the properties andcouplings of the top quark to high precision. Precision knowledgeof the top quark serves as a telescope for new physics for scalesof up to 100 TeV. The talk includes bothcontinuum production of top quarks as well as the production atvery low velocities very near to the top threshold, describing techniquesof fixed-order perturbative calculations in the SM as well as resummationof large logarithms close to the threshold and their combination. I willalso briefly mention the connection to automated tools for precisionsimulations of SM processes for e+e- colliders
Measurement of electroweak production of a Wboson in association with two jets in proton–proton collisions at s√=13TeV
No full textA measurement is presented of electroweak (EW) production of a W boson in association with two jets in proton–proton collisions at s√=13TeV. The data sample was recorded by the CMS Collaboration at the LHC and corresponds to an integrated luminosity of 35.9fb−1. The measurement is performed for the ℓνjj final state (with ℓν indicating a lepton–neutrino pair, and j representing the quarks produced in the hard interaction) in a kinematic region defined by invariant mass mjj>120GeV and transverse momenta pTj>25GeV. The cross section of the process is measured in the electron and muon channels yielding σEW(Wjj)=6.23±0.12(stat)±0.61(syst)pb per channel, in agreement with leading-order standard model predictions. The additional hadronic activity of events in a signal-enriched region is studied, and the measurements are compared with predictions. The final state is also used to perform a search for anomalous trilinear gauge couplings. Limits on anomalous trilinear gauge couplings associated with dimension-six operators are given in the framework of an effective field theory. The corresponding 95% confidence level intervals are −2.3<cWWW/Λ2<2.5TeV−2, −8.8<cW/Λ2<16TeV−2, and −45<cB/Λ2<46TeV−2. These results are combined with the CMS EW Zjj analysis, yielding the constraint on the cWWW coupling: −1.8<cWWW/Λ2<2.0TeV−2
Microstructure Evolution and Competitive Reactions during Quenching and Partitioning of a Model Fe–C–Mn–Si Alloy
No full textThe mechanisms behind the carbon enrichment of austenite during quenching andpartitioning are still a matter of debate. This work investigates the microstructural evolution duringthe quenching and partitioning of a model Fe–C–Mn–Si alloy by means of in situ high energy X‐raydiffraction (HEXRD) atom probe tomography, and image analysis. The ultra‐fast time‐resolvedquantitative information about phase transformations coupled with image analysis highlights theformation of carbide‐free BCT bainite, which is formed within a very short range during thereheating and partitioning step. Its transformation rate, which is a better indicator than the intrinsicvolume fraction, depends on the quenching temperature (QT). It is shown to decrease withdecreasing QT, from 45% at QT = 260 °C to 20% at QT = 200 °C. As a consequence, a significant partof the carbon enrichment observed in austenite can be attributed to bainite transformation.Furthermore, a large part of carbon was shown to be trapped into martensite. Both the formation ofFe 2.6 C iron carbides and the segregation of carbon on lath boundaries in martensite were highlightedby atom probe tomography. The energy for carbon segregation was determined to be 0.20 eV, andthe carbon concentration on the lath boundaries was obtained to be around 25 at %. Therefore, thecarbon enrichment of austenite is the result of competitive reactions such as carbon partitioningfrom martensite, bainite transformation, and carbon trapping in martensite
